# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
import argparse
import multiprocessing
import time
import weakref
from collections.abc import Sequence
from multiprocessing import connection
from multiprocessing.process import BaseProcess
from typing import (TYPE_CHECKING, Any, Callable, Generic, Optional, TypeVar,
                    Union, overload)

import torch

from vllm.logger import init_logger
from vllm.usage.usage_lib import (UsageContext, is_usage_stats_enabled,
                                  usage_message)
from vllm.utils import (bind_process_name, get_open_port,
                        get_open_zmq_ipc_path, get_tcp_uri, kill_process_tree)

if TYPE_CHECKING:
    from vllm.v1.engine.coordinator import DPCoordinator
    from vllm.v1.engine.utils import (CoreEngineActorManager,
                                      CoreEngineProcManager)

logger = init_logger(__name__)

T = TypeVar("T")


class ConstantList(Generic[T], Sequence):

    def __init__(self, x: list[T]) -> None:
        self._x = x

    def append(self, item):
        raise Exception("Cannot append to a constant list")

    def extend(self, item):
        raise Exception("Cannot extend a constant list")

    def insert(self, item):
        raise Exception("Cannot insert into a constant list")

    def pop(self, item):
        raise Exception("Cannot pop from a constant list")

    def remove(self, item):
        raise Exception("Cannot remove from a constant list")

    def clear(self):
        raise Exception("Cannot clear a constant list")

    def index(self,
              item: T,
              start: int = 0,
              stop: Optional[int] = None) -> int:
        return self._x.index(item, start,
                             stop if stop is not None else len(self._x))

    @overload
    def __getitem__(self, item: int) -> T:
        ...

    @overload
    def __getitem__(self, s: slice, /) -> list[T]:
        ...

    def __getitem__(self, item: Union[int, slice]) -> Union[T, list[T]]:
        return self._x[item]

    @overload
    def __setitem__(self, item: int, value: T):
        ...

    @overload
    def __setitem__(self, s: slice, value: T, /):
        ...

    def __setitem__(self, item: Union[int, slice], value: Union[T, list[T]]):
        raise Exception("Cannot set item in a constant list")

    def __delitem__(self, item):
        raise Exception("Cannot delete item from a constant list")

    def __iter__(self):
        return iter(self._x)

    def __contains__(self, item):
        return item in self._x

    def __len__(self):
        return len(self._x)

    def __repr__(self):
        return f"ConstantList({self._x})"


def get_engine_client_zmq_addr(local_only: bool,
                               host: str,
                               port: int = 0) -> str:
    """Assign a new ZMQ socket address.

    If local_only is True, participants are colocated and so a unique IPC
    address will be returned.

    Otherwise, the provided host and port will be used to construct a TCP
    address (port == 0 means assign an available port)."""

    return get_open_zmq_ipc_path() if local_only else (get_tcp_uri(
        host, port or get_open_port()))


class APIServerProcessManager:
    """Manages a group of API server processes.
    
    Handles creation, monitoring, and termination of API server worker
    processes. Also monitors extra processes to check if they are healthy.
    """

    def __init__(
        self,
        target_server_fn: Callable,
        listen_address: str,
        sock: Any,
        args: argparse.Namespace,
        num_servers: int,
        input_addresses: list[str],
        output_addresses: list[str],
        stats_update_address: Optional[str] = None,
    ):
        """Initialize and start API server worker processes.
        
        Args:
            target_server_fn: Function to call for each API server process
            listen_address: Address to listen for client connections
            sock: Socket for client connections
            args: Command line arguments
            num_servers: Number of API server processes to start
            input_addresses: Input addresses for each API server
            output_addresses: Output addresses for each API server
            stats_update_address: Optional stats update address 
        """
        self.listen_address = listen_address
        self.sock = sock
        self.args = args
        bind_process_name(self.__class__.__name__)
        # Start API servers
        spawn_context = multiprocessing.get_context("spawn")
        self.processes: list[BaseProcess] = []

        for i, in_addr, out_addr in zip(range(num_servers), input_addresses,
                                        output_addresses):
            client_config = {
                "input_address": in_addr,
                "output_address": out_addr,
                "client_index": i
            }
            if stats_update_address is not None:
                client_config["stats_update_address"] = stats_update_address

            proc = spawn_context.Process(target=target_server_fn,
                                         name=f"ApiServer_{i}",
                                         args=(listen_address, sock, args,
                                               client_config))
            self.processes.append(proc)
            proc.start()

        logger.info("Started %d API server processes", len(self.processes))

        # Shutdown only the API server processes on garbage collection
        # The extra processes are managed by their owners
        self._finalizer = weakref.finalize(self, shutdown, self.processes)

    def close(self) -> None:
        self._finalizer()


def wait_for_completion_or_failure(
        api_server_manager: APIServerProcessManager,
        engine_manager: Optional[Union["CoreEngineProcManager",
                                       "CoreEngineActorManager"]] = None,
        coordinator: Optional["DPCoordinator"] = None) -> None:
    """Wait for all processes to complete or detect if any fail.
    
    Raises an exception if any process exits with a non-zero status.

    Args:
        api_server_manager: The manager for API servers.
        engine_manager: The manager for engine processes.
            If CoreEngineProcManager, it manages local engines;
            if CoreEngineActorManager, it manages all engines.
        coordinator: The coordinator for data parallel.
    """

    from vllm.v1.engine.utils import (CoreEngineActorManager,
                                      CoreEngineProcManager)

    try:
        logger.info("Waiting for API servers to complete ...")
        # Create a mapping of sentinels to their corresponding processes
        # for efficient lookup
        sentinel_to_proc: dict[Any, BaseProcess] = {
            proc.sentinel: proc
            for proc in api_server_manager.processes
        }

        if coordinator:
            sentinel_to_proc[coordinator.proc.sentinel] = coordinator.proc

        actor_run_refs = []
        if isinstance(engine_manager, CoreEngineProcManager):
            for proc in engine_manager.processes:
                sentinel_to_proc[proc.sentinel] = proc
        elif isinstance(engine_manager, CoreEngineActorManager):
            actor_run_refs = engine_manager.get_run_refs()

        # Check if any process terminates
        while sentinel_to_proc or actor_run_refs:
            # Wait for any process to terminate
            ready_sentinels: list[Any] = connection.wait(sentinel_to_proc,
                                                         timeout=5)

            # Process any terminated processes
            for sentinel in ready_sentinels:
                proc = sentinel_to_proc.pop(sentinel)

                # Check if process exited with error
                if proc.exitcode != 0:
                    raise RuntimeError(
                        f"Process {proc.name} (PID: {proc.pid}) "
                        f"died with exit code {proc.exitcode}")

            if actor_run_refs:
                import ray
                _, actor_run_refs = ray.wait(actor_run_refs, timeout=5)

    except KeyboardInterrupt:
        logger.info("Received KeyboardInterrupt, shutting down API servers...")
    except Exception as e:
        logger.exception("Exception occurred while running API servers: %s",
                         str(e))
        raise
    finally:
        logger.info("Terminating remaining processes ...")
        api_server_manager.close()
        if coordinator:
            coordinator.close()
        if engine_manager:
            engine_manager.close()


# Note(rob): shutdown function cannot be a bound method,
# else the gc cannot collect the object.
def shutdown(procs: list[BaseProcess]):
    # Shutdown the process.
    for proc in procs:
        if proc.is_alive():
            proc.terminate()

    # Allow 5 seconds for remaining procs to terminate.
    deadline = time.monotonic() + 5
    for proc in procs:
        remaining = deadline - time.monotonic()
        if remaining <= 0:
            break
        if proc.is_alive():
            proc.join(remaining)

    for proc in procs:
        if proc.is_alive() and (pid := proc.pid) is not None:
            kill_process_tree(pid)


def copy_slice(from_tensor: torch.Tensor, to_tensor: torch.Tensor,
               length: int) -> torch.Tensor:
    """
    Copy the first length elements of a tensor into another tensor in a
    non-blocking manner.

    Used to copy pinned CPU tensor data to pre-allocated GPU tensors.

    Returns the sliced target tensor.
    """
    return to_tensor[:length].copy_(from_tensor[:length], non_blocking=True)


def report_usage_stats(
        vllm_config,
        usage_context: UsageContext = UsageContext.ENGINE_CONTEXT) -> None:
    """Report usage statistics if enabled."""

    if not is_usage_stats_enabled():
        return

    from vllm.model_executor.model_loader import get_architecture_class_name

    usage_message.report_usage(
        get_architecture_class_name(vllm_config.model_config),
        usage_context,
        extra_kvs={
            # Common configuration
            "dtype":
            str(vllm_config.model_config.dtype),
            "tensor_parallel_size":
            vllm_config.parallel_config.tensor_parallel_size,
            "block_size":
            vllm_config.cache_config.block_size,
            "gpu_memory_utilization":
            vllm_config.cache_config.gpu_memory_utilization,

            # Quantization
            "quantization":
            vllm_config.model_config.quantization,
            "kv_cache_dtype":
            str(vllm_config.cache_config.cache_dtype),

            # Feature flags
            "enable_lora":
            bool(vllm_config.lora_config),
            "enable_prefix_caching":
            vllm_config.cache_config.enable_prefix_caching,
            "enforce_eager":
            vllm_config.model_config.enforce_eager,
            "disable_custom_all_reduce":
            vllm_config.parallel_config.disable_custom_all_reduce,
        })
